Process of making aldols



Patented Aug. 31, 1926. i l

UNITED'STATES PATENT OFFICE.

CLARENCE J. HERRLY, OF NIAGARA FALLS, NEW YORK, ASSIGN OR TO CARBIDE AND CARBON CHEMICALS CORPORATION, CORPORATION OF NEW YORK.

PROCESS OF MAKING ALDOLS.

No Drawing. Application filed May 22', 1924. Serial No. 715,236.

This invention relatesto improvements in overheated batch has been suggested. This the manufacture of condensation products results in undesired condensations and makes of aliphatic aldehydes. The invention rethe material substantially useless. 55 lates primarily to that type of reaction in- Also, a large proportion of alkali entails d-uced by caustic alkali and other substances the formation of correspondingly large acting upon aldehydes, and known as the amounts of saltswhen the batch is neutralaldol condensation. This, in the case of ized after the reaction is complete. Such acetaldehyde, may be represented by the folsalts are troublesome to remove and may 60 lowing equation, showing the formation of have a deleterious effect on the conversion of aldol (,B-hydroxy butyraldehyde) the aldol into the desired final product, for

' exam l'e crotonaldehyde. 1 2CH3CHOCH8'CHOH'CH2'CHO Thie above-mentioned difliculties are avoid- In the production of this substance, using ed and positive advantages are obtained by 65 caustic alkali as the condenslng agent, 1t has the present process, of which the following heretofore been considered necessary to keep example is illustrative:

the reaction temperature below (3., to Acct-aldehyde, is drawn into a closed vessel prevent too 'violent action. It is usual to provided withan agitator and cooling coil. soeclfy temperatures between 0 C. and 10 A dilute aqueous solution of a caustic alkali, Alkali in amount about 0.5% to 10% of preferably sodium hydrozgid, is added in 20 the Weight of the aldehyde is ordinarily used small portions to neutralize the ascertained to bring about the condensation. acidity of the aldehyde. This acidity is due ave discovered that the reaction is more chiefly to oxidation by the air, and it is prereadlly controlled and that better yields are ferred to produ6e,,keepf,and use the aldehyde W obtamed when the alkali concentration is in an atmosphere of nitrogen, acetylene, or relatively low and the temperature high, as other suitable non-oxidizing gas.

eompared with previous processes. In ac- During the neutralization the batch is cordance with a preferred utilization of the preferably cooled to about 10 C. Ihave invention, the free alkali is not in material discovered that in the absence of such cooll0 excess of 0.1% and the temperature of the ing the alkali intended for neutralization is reaction mixture is allowed to rise to about likely to initiate aldol formation in limited .or C. portions of the batch, even though efficient This procedure results in yields of aldol stirring means, be used. This results in ir' averaging 10 to 15% more than are .ordinaregularity'of reaction which may be objec- 88 v rily obtainable with the low temperature, tionableand justifies the preliminary c001 35 high alkali processes. ing. p

In addition, the serious disadvantages of The cold,-neutral aldehyde is nextinade those processes are. substantially avoided. faintly alkaline to phenolphthalein by addi- Aside from the relatively low yield, the tion of about 0.05% by weight of caustic al 90 principal of these disadvantages are the kali in dilute aqueous solution. The temslowness of the reaction, the tendency to perature is allowed to rise and the aldol conresin formation, and the danger of a reacdensation proceeds smoothly and at a rapid tion of explosive violence in case the temrate. When the temperature approaches 40 per-ature control should fail. Temperature C. cold water or. brine should be circulated control is ditficult when using a high perthrough the cooling coil to hold the batch at 45 centage of alkali, on account of the great .inabout that point.

crease in the velocity of the reaction-caused The period of reaction maybe approxiby slight rise of temperature This ditficulty mately nine hours. The batch is then cooled is especially noticeable when working with to around 20 C. and dilute sulfuric acid, 109 large bate es, and serious accidents are not equivalent to the total amount of alkali used,

unlikely if acetaldehyde containing a high is added. If acetates will not-be objectionpercentage of alkali becomes overheated. To able, the sulfuric acid need be equivalent avoid this danger, addition of acid to the only to the alkali added after the initial neuis returned to the process.

It will be understood that the preceding description is merely illustrative. Numerbus modifications may be made. For example, I may use only 0.01% alkali as .the condensing agent. With such low concentration a somewhat longer reaction period is desirable. The completion of the reaction may be ascertained by taking the specific gravity of the batch, or in other suitable Ways. When the specific gravity is about C. the maximum .aldol condensation has usually been obtained.

I prefer aqueous caustic alkali, but soluti us of such alkali in organic solvents, with 0 without water, or even solid alkalies, are not precluded. However, alcoholic solutions frequently cause the formation of acetals, which are objectionable and can not practically be removed. Solid alkalies tend to act onlocalized areas of the batch, even with efiicient stirring.

The pressure prevailing in the closed reaction vesselis ordinarily about atmospheric. Thereaction proceeds satisfactorily under this condition, but greater or less pressures may be used if desired.- Variation in the pressure may necessitate a corresponding change in the temperature.

While reference has been made particularly to condensation-of acetaldehyde, various other aliphatic aldehydes ma be condense in the manner described. rotonaldehyde and butyraldehyde, for example, give excellent yields of the corresponding aldols.

I am' aware that statements occur in the literature to the effect that aldol can not be produced by caustic alkali in amounts ap proximating 0.1% or less. My researches show that such statements are erroneous.

The "novel processes described herein have claimed in my application The acetaldehyde distilled off given highly satisfactory results in operations on a commercial scale.

Iclaim:

1. Process of making an aldol from an aliphatic aldehyde containing a plurality of} carbon atoms in its molecule, comprising adding to the substantially neutral aldehyde between about 0.01% and 0.10% by weight of caustic alkali, and permitting a reaction temperature in material excess of 20 C. for a suitable period.

2. Process of preparing an aliphatic aldehyde for a condensation reaction, comprising neutralizing any acidity of the aldehyde while maintaining a temperature not materially in excess of 10 0., whereby premature condensation is prevented.

3. Process of making an aldol from an aliphatic aldehyde containing a plurality of carbon atoms in its molecule, comprising neutralizing any acidity of the aldehyde while maintaining a temperature not mate rially in excess of 10 C., adding to the substantially neutral aldehyde between about 0.01% and 0.10% by weight of caustic alkali,

and permitting a reaction temperature in material 'excess of 20 C. for a suitable period.

4. Process. of making an aldol from an aliphatic aldehyde containing a plurality of carbon atoms in its molecule, comprising adding to the substantially neutral aldehyde about 0.01% to 0.10% by weight of caustic alkali in dilute aqueous solution, and conducting the greater part of the condensation reaction at'a temperature between 30 C. and C. I

' 5. lgrocess of making an aldol from an aliphatic-aldehyde containing a plurality of carbon atoms in its molecule, comprising adding to the substantially neutral aldehyde about 0.05% by weight of caustic alkali in dilute aqueous solution, reaction to take place at a temperature of d about 40 C.

6. Process of making aldol, comprising adding to acetaldehyde substantially free from uncombined acetic acid, about 0.01% to 0.10% by weight of caustic alkali in dilute aqueous solution, and, permitting reaction to take place at atemperature materially in excessof 20 C. for a suitable period.

In testimony whereof, I afiix my signature.

CLARENCE J. HERRLY.

and permitting the p 

